Impact of the Mean Cochlear Biologically Effective Dose on Hearing Preservation After Stereotactic Radiosurgery for Vestibular Schwannoma: A Retrospective Longitudinal Analysis.

BACKGROUND AND OBJECTIVES: Stereotactic radiosurgery (SRS) is a useful alternative for small- to medium-sized vestibular schwannoma. To evaluate whether biologically effective dose (BED Gy2.47 ), calculated for mean (BED Gy2.47 mean) and maximal (BED Gy2.47 max) cochlear dose, is relevant for hearing preservation. METHODS: This is a retrospective longitudinal single-center study. Were analyzed 213 patients with useful baseline hearing. Risk of hearing decline was assessed for Gardner-Robertson classes and pure tone average (PTA) loss. The mean follow-up period was 39 months (median 36, 6-84). RESULTS: Hearing decline (Gardner-Robertson class) 3 years after SRS was associated with higher cochlear BED Gy2.47 mean (odds ratio [OR] 1.39, P = .009). Moreover, BED Gy2.47 mean was more relevant as compared with BED Gy2.47 max (OR 1.13, P = .04). Risk of PTA loss (continuous outcome, follow-up minus baseline) was significantly corelated with BED Gy2.47 mean at 24 (beta coefficient 1.55, P = .002) and 36 (beta coefficient 2.01, P = .004) months after SRS. Risk of PTA loss (>20 dB vs ≤) was associated with higher BED Gy2.47 mean at 6 (OR 1.36, P = .002), 12 (OR 1.36, P = .007), and 36 (OR 1.37, P = .02) months. Risk of hearing decline at 36 months for the BED Gy2.47 mean of 7-8, 10, and 12 Gy 2.47 was 28%, 57%, and 85%, respectively. CONCLUSION: Cochlear BED Gy2.47 mean is relevant for hearing decline after SRS and more relevant as compared with BED Gy2.47 max. Three years after SRS, this was sustained for all hearing decline evaluation modalities. Our data suggest the BED Gy2.47 mean cut-off of ≤8 Gy 2.47 for better hearing preservation rates .

The Relevance of Biologically Effective Dose for Hearing Preservation After Stereotactic Radiosurgery for Vestibular Schwannomas: A Retrospective Longitudinal Study.

BACKGROUND: Stereotactic radiosurgery has become a common treatment approach for small-to-medium size vestibular schwannomas. OBJECTIVE: To evaluate relationship between time (beam-on and treatment) and risk of hearing decline after stereotactic radiosurgery for vestibular schwannomas in patients with Gardner-Robertson (GR) baseline classes I and II. METHODS: This retrospective longitudinal single-center study included 213 patients with GR I and II treated between June 2010 and December 2019. Risk of passing from GR classes I and II (coded 0) to other classes III, IV, and V (coded 1) and the increase in pure tone average (continuous outcome) were evaluated using a mixed-effect regression model. Biologically effective dose (BED) was further assessed for an alpha/beta ratio of 2.47 (Gy 2.47 ). RESULTS: Binary outcome analysis revealed sex, dose rate, integral dose, time [beam-on time odds ratio 1.03, P = .03, 95% CI 1.00-1.06; treatment time ( P = .02) and BED ( P = .001) as relevant. Fitted multivariable model included the sex, dose rate, and BED. Pure tone average analysis revealed age, integral dose received by tumor, isocenter number, time (beam-on time odds ratio 0.20, P = .001, 95% CI 0.083-0.33) and BED ( P = .005) as relevant. CONCLUSION: Our analysis showed that risk of hearing decline was associated with male sex, higher radiation dose rate (cutoff 2.5 Gy/minute), higher integral dose received by the tumor, higher beam-on time ≥20 minutes, and lower BED. A BED between 55 and 61 was considered as optimal for hearing preservation.